The Integrity of the Cell Wall and Its Remodeling during Heterocyst Differentiation Are Regulated by Phylogenetically Conserved Small RNA Yfr1 in Nostoc sp. Strain PCC 7120

Yfr1 is a strictly conserved small RNA in cyanobacteria. A bioinformatic prediction to identify possible interactions of Yfr1 with mRNAs was carried out by using the sequences of Yfr1 from several heterocyst-forming strains, including Nostoc sp. strain PCC 7120. The results of the prediction were enriched in genes encoding outer membrane proteins and enzymes related to peptidoglycan biosynthesis and turnover. Heterologous expression assays with Escherichia coli demonstrated direct interactions of Yfr1 with mRNAs of 11 of the candidate genes. The expression of 10 of them (alr2458, alr4550, murC, all4829, all2158, mraY, alr2269, alr0834, conR, patN) was repressed by interaction with Yfr1, whereas the expression of amiC2, encoding an amidase, was increased. The interactions between Yfr1 and the 11 mRNAs were confirmed by site-directed mutagenesis of Yfr1. Furthermore, a Nostoc strain with reduced levels of Yfr1 had larger amounts of mraY and murC mRNAs, supporting a role for Yfr1 in the regulation of those genes. Nostoc strains with either reduced or increased expression of Yfr1 showed anomalies in cell wall completion and were more sensitive to vancomycin than the wild-type strain. Furthermore, growth in the absence of combined nitrogen, which involves the differentiation of heterocysts, was compromised in the strain overexpressing Yfr1, and filaments were broken at the connections between vegetative cells and heterocysts. These results indicate that Yfr1 is an important regulator of cell wall homeostasis and correct cell wall remodeling during heterocyst differentiation.IMPORTANCE Bacterial small RNAs (sRNAs) are important players affecting the regulation of essentially every aspect of bacterial physiology. The cell wall is a highly dynamic structure that protects bacteria from their fluctuating environment. Cell envelope remodeling is particularly critical for bacteria that undergo differentiation processes, such as spore formation or differentiation of heterocysts. Heterocyst development involves the deposition of additional layers of glycolipids and polysaccharides outside the outer membrane. Here, we show that a cyanobacterial phylogenetically conserved small regulatory RNA, Yfr1, coordinates the expression of proteins involved in cell wall-related processes, including peptidoglycan metabolism and transport of different molecules, as well as expression of several proteins involved in heterocyst differentiation.España Ministerio de Educación, Cultura y Deporte (FPU014/05123 and EST16-00088)España Ministerio de Economía y Competitividad BFU2013-48282-C2-1España Agencia Estatal de Investigación (AEI), Ministerio de Economía, Industria y Competitividad, both cofinanced by the Fondo Europeo de Desarrollo Regional (FEDER) BFU2016-74943-C2-1-

A combinatorial strategy of alternative promoter use during differentiation of a heterocystous cyanobacterium

Heterocystous cyanobacteria such as Nostoc sp. are filamentous photosynthetic organisms that, in response to nitrogen deficiency, undergo a differentiation process transforming certain, semi-regularly spaced cells into heterocysts, devoted to nitrogen fixation. During transition to a nitrogen-fixing regime, growth of most vegetative cells in the filament is temporarily arrested due to nutritional deprivation, but developing heterocysts require intense transcriptional activity. Therefore, the coexistence of arrested vegetative cells and actively developing prospective heterocysts relies on the simultaneous operation of somewhat opposite transcriptional programs. We have identified genes with multiple nitrogen-responsive transcriptional starts appearing in seemingly paradoxical combinations. For instance, sigA, encoding the RNA polymerase housekeeping sigma factor, is transcribed from one major nitrogen stress-repressed promoter and from a second, nitrogen stress-induced promoter. Here, we show that both promoters are expressed with complementary temporal dynamics. Using a gfp reporter we also show that transcription from the inducible promoter takes place exclusively in differentiating heterocysts and is already detected before any morphological or fluorescence signature of differentiation is observed. Tandem promoters with opposite dynamics could operate a compensatory mechanism in which repression of transcription from the major promoter operative in vegetative cells is offset by transcription from a new promoter only in developing heterocyst.Ministerio de Economía y Competitividad BFU2013-48282-C2-1Agencia Estatal de Investigación (AEI) BFU2016-74943-C2-1-PMinisterio de Educación, Cultura y Deportes FPU014/0512

La importancia geopolítica del sector agropecuario en la seguridad energética a raíz de la guerra entre Rusia y Ucrania el papel de los biocombustibles

Aborda el conflicto bélico entre la Federación Rusa y Ucrania y cómo abre la discusión global a la seguridad energética. Esta situación se enmarca en las recientes sanciones políticas y económicas impuestas por la comunidad internacional hacia Rusia, entre las cuales se prohíbe la importación de su petróleo. En este contexto, los biocombustibles, especialmente los líquidos, por su alto nivel de inserción actual cobran una importancia estratégica para substituir parte de los consumos de petróleo y derivados. Por otra parte, el sector agropecuario en las Américas aparece como un sector que no solamente contribuye a garantizar la seguridad alimentaria, sino que también hace su aporte a fortalecer la seguridad energética. Se observan oportunidades para la expansión en la producción de biocombustibles líquidos en el continente para reforzar la seguridad energética. De la misma forma, la crisis en el sector del gas natural puede ser una bisagra para la apertura de políticas que promuevan el uso del biogás a nivel mundial

The role of liquid biofuels in the energy transition

Dentro del paradigma técnico productivo de la bioeconomía, se destaca el sendero de los biocombustibles líquidos en la transición climática y energética del sector transporte. Esto debido a la posibilidad de utilización de diversos biocombustibles líquidos en reemplazo de fósiles, ya que los últimos se han constituido como una transición más limpia que permite reducir las emisiones de gases de efecto invernadero del sector, el cual tiene fuertes compromisos medioambientales. Adicionalmente, los biocombustibles líquidos serán un complemento tanto a otros paradigmas tecnológicos en desarrollo (electromovilidad, hidrógeno, etc.), como a la movilidad terrestre, aérea y marítima. En la medida que estas tecnologías atraviesan su proceso de instalación en el mercado y posterior masificación (para lo cual se requerirán varias décadas), los biocombustibles líquidos permiten avanzar en una matriz de consumo de combustibles más limpia.Within the productive technical paradigm of bioeconomy, the path of liquid biofuels in the climate and energy transition of the transport sector stands out. Due to the possibility of using various liquid biofuels, replacing fossils with no or few technical adaptations in the engines, these have become a cleaner transition that allows reducing greenhouse gas emissions in the sector, which has strong environmental commitments. Additionally, liquid biofuels will be a complement to other technological paradigms under development (electromobility, hydrogen, etc.), both in land, air and maritime mobility. In the meantime, while these technologies go through their installation process in the market and subsequent massification (which will require several decades), liquid biofuels allow progress in a cleaner fuel consumption matri

El aporte de la agricultura hacia una transición limpia en el sector transporte

El sector de transporte te terrestre es uno de los principales emisores de CO2, lo que ha hecho necesaria la búsqueda de nuevas tecnologías que permiten un desarrollo más sostenible. A pesar de la existencia de tecnologías limpias como la electricidad y el uso de hidrógeno, se extensión y asequibilidad han limitado su extensión, ante lo cual, los biocombustibles líquidos se han convertido en una opción viable en el proceso de transición. A partir del 2020 se ha notado un mayor uso de biocombustibles en distintos sectores y se ha proyectado, que, en un futuro, logre posicionarse como una tecnología de mayor importancia en la industria del transporte terrestre y de aviación

Identification of conserved and potentially regulatory small RNAs in heterocystous cyanobacteria

Small RNAs (sRNAs) are a growing class of non-protein-coding transcripts that participate in the regulation of virtually every aspect of bacterial physiology. Heterocystous cyanobacteria are a group of photosynthetic organisms that exhibit multicellular behavior and developmental alternatives involving specific transcriptomes exclusive of a given physiological condition or even a cell type. In the context of our ongoing effort to understand developmental decisions in these organisms we have undertaken an approach to the global identification of sRNAs. Using differential RNA-Seq we have previously identified transcriptional start sites for the model heterocystous cyanobacterium Nostoc sp. PCC 7120. Here we combine this dataset with a prediction of Rho-independent transcriptional terminators and an analysis of phylogenetic conservation of potential sRNAs among 89 available cyanobacterial genomes. In contrast to predictive genome-wide approaches, the use of an experimental dataset comprising all active transcriptional start sites (differential RNA-Seq) facilitates the identification of bona fide sRNAs. The output of our approach is a dataset of predicted potential sRNAs in Nostoc sp. PCC 7120, with different degrees of phylogenetic conservation across the 89 cyanobacterial genomes analyzed. Previously described sRNAs appear among the predicted sRNAs, demonstrating the performance of the algorithm. In addition, new predicted sRNAs are now identified that can be involved in regulation of different aspects of cyanobacterial physiology, including adaptation to nitrogen stress, the condition that triggers differentiation of heterocysts (specialized nitrogen-fixing cells). Transcription of several predicted sRNAs that appear exclusively in the genomes of heterocystous cyanobacteria is experimentally verified by Northern blot. Cell-specific transcription of one of these sRNAs, NsiR8 (nitrogen stress-induced RNA 8), in developing heterocysts is also demonstrate

Safety assessment of chronic oral exposure to iron oxide nanoparticles

Iron oxide nanoparticles with engineered physical and biochemical properties are finding a rapidly increasing number of biomedical applications. However, a wide variety of safety concerns, especially those related to oral exposure, still need to be addressed for iron oxide nanoparticles in order to reach clinical practice. Here, we report on the effects of chronic oral exposure to low doses of γ-Fe2O3 nanoparticles in growing chickens. Animal observation, weight, and diet intake reveal no adverse signs, symptoms, or mortality. No nanoparticle accumulation was observed in liver, spleen, and duodenum, with feces as the main excretion route. Liver iron level and duodenal villi morphology reflect the bioavailability of the iron released from the partial transformation of γ-Fe2O3 nanoparticles in the acid gastric environment. Duodenal gene expression studies related to the absorption of iron from γ-Fe2O3 nanoparticles indicate the enhancement of a ferric over ferrous pathway supporting the role of mucins. Our findings reveal that oral administration of iron oxide nanoparticles is a safe route for drug delivery at low nanoparticle doses.Peer Reviewe

Combining Grape Byproducts to Maximise Biological Activity of Polyphenols in Chickens

Grape seeds (GS) and grape skins (GK) are natural sources of polyphenols with antioxidant capacity. An experiment was conducted to investigate in chickens the effect of including GS and GK (40 g/kg), individually or combined in different proportions (20 g/kg GS–20 g/kg GK; 30 g/kg GS–10 g/kg GK; 10 g/kg GS–30 g/kg GK), in a corn-soybean diet on growth performance, ileal and excreta contents of total extractable polyphenols (TEP) and tannins, ileal digestibility of protein, plasma and meat α-tocopherol concentration and lipid oxidation (assessed by measuring the thiobarbituric acid reactive substances, TBARS) of stored thigh meat. Neither growth performance parameters nor ileal digestibility of protein were affected by dietary treatments. As compared with control birds, chickens fed the grape byproduct diets showed higher ileal (p < 0.001) and excreta (p < 0.001) TEP and tannins contents. Dietary inclusion of grape byproducts increased α-tocopherol concentration both in plasma (p < 0.001) and in thigh meat (p < 0.01 at 1 d; p < 0.001 at 7 d), as compared with the control group. The highest plasma α-tocopherol concentrations were reached with the 30 g/kg GS–10 g/kg GK and 20 g/kg GS–20 g/kg GK combinations. On day 1 of meat storage, no differences on meat α-tocopherol concentration were found among the grape byproducts treatments but on day 7 of storage, the 20 g/kg GS–20 g/kg GK and 10 g/kg GS–30 g/kg GK combinations led to the highest α-tocopherol concentrations in chicken thigh meat. After seven days of refrigerated storage of meat, the TBARS value was lower in chickens fed the grape byproducts diets than in control birds (1.27 vs. 2.49 mg MDA/kg, p < 0.001). Moreover, among the different grape byproduct treatments, the lowest MDA values were reached with the diets containing GK at rates from 20 to 40 g/kg. In conclusion, dietary incorporation of 40 g/kg of GS and GK added separately or combined increased the plasma and meat α-tocopherol content. Furthermore, the combinations of GS and GK with a proportion of GK of at least 50% optimised α-tocopherol concentration both in plasma and in thigh meat and mitigated lipid oxidation in 7-day stored meat